Routing, Spectrum, and Transponder Assignment (RSTA) in Elastic Optical Networks

Backbone networks are evolving toward Elastic Optical Network (EON) architecture that allows a flexible and efficient use of spectrum resources. Flexibility in EONs is guaranteed also by emerging sliceable bandwidth variable transponders (SBVTs) that support the simultaneous generation of multiple optical carriers. Such carriers can be used to serve different lightpaths (i.e., slice-ability), or can be merged into a single high-rate super-channel. SBVTs typically use a dedicated laser to generate each carrier, i.e., multi-lasers SBVT (ML-SBVT). Alternatively, a multi-wavelength source can be used to generate multiple carriers using a single laser, i.e., multi-wavelength SBVT (MW-SBVT). Using MW-SBVT improves the super-channel spectrum efficiency. Indeed, MW-SBVT reduces the intercarrier interference among the sub-carriers composing the super-channel, thus it is possible to reduce the guard bands among sub-carriers. With ML-SBVT, each sub-carrier suffers from unstableness of the related laser and inter-carrier interference may have a huge impact, thus higher guard bands are needed. On the other hand, the use of a MWSBVT introduces specific constraints to the routing and spectrum assignment (RSA) because the spacing among the sub-carriers is limited to a range of specific values. To take into account the constraints introduced by transponders, this paper integrates the selection of the transponder into RSA thus proposing a dynamic routing, spectrum, and transponder assignment (RSTA) scheme supporting both ML-SBVT and MW-SBVT technologies, and aiming to combine the benefits of the two technologies. Simulation results show that the proposed RSTA scheme provides benefits in terms of achieved blocking probability compared to traditional RSA schemes. Moreover, the achieved results demonstrate that by jointly using both SBVT technologies provides significant benefits with respect to the utilization of any single SBVT technology.